DHA and EPA in the form of dietary fish or fish oil supplements lowers triglycerides, reduces the risk of death, heart attack, dangerous abnormal heart rhythms, and strokes in people with known cardiovascular disease, slows the buildup of atherosclerotic plaques ("hardening of the arteries"), and lowers blood pressure slightly.

However, high doses may have harmful effects, such as an increased risk of bleeding. Although similar benefits are proposed for alpha-linolenic acid, scientific evidence is less compelling, and beneficial effects may be less pronounced.

This fish oil could potentially save more lives than cardiac defibrillators, devices used to revive individuals whose hearts have stopped beating and to prevent and treat life-threatening heart arrhythmias, researchers estimate in a new report.

Past research has linked the omega-3 fatty acids found in oily fish to a lower risk of fatal heart rhythm disturbances. This latest study tried to estimate the potential public health impact of raising adults' omega-3 levels with fish oil supplements.

Using a computer-simulated community of 100,000 Americans and data from past medical studies, the researchers calculated that raising omega-3 levels would save 58 lives each year.

This amounts to a 6.4-percent total death reduction -- mostly by preventing sudden cardiac death in apparently people, according to the study authors, led by Dr. Thomas E. Kottke of the Heart Center at Regions Hospital in St. Paul, Minnesota.

Conversely, the researchers estimate that far fewer lives would be saved by defibrillators, devices that deliver a "shock" to restart the heart or to resolve ventricular fibrillation, an otherwise fatal heartbeat irregularity in which the heart quivers instead of contracting normally.

For example, the study found, even if automated external defibrillators (AEDs) were available in every home and public area, the devices would lower a community's annual death rate by less than 1 percent.

AEDs are portable devices that can be used by lay people to shock someone in cardiac arrest. They are frequently available in public places such as large stores or on airplanes. Though the devices do save lives, the researchers note that AEDs would make little difference in the overall rate of sudden cardiac death.

Kottke's team estimates that implantable defibrillators would lower the cardiac death rate by 3.3 percent, still not as much as the 6.6-percent lower death rate achieved by increasing the use of fish oil supplements.

Though the implantable devices are effective, the researchers point out that about half of adults who die suddenly from cardiac arrest have no warning signs beforehand -- and would, therefore, never be candidates for an implanted defibrillator.

The study, which is published in the American Journal of Preventive Medicine, has its limitations, as a computer simulation. Though the researchers based their estimates of fish oil benefits on two large studies, it's not yet clear that omega-3 fatty acids prevent sudden cardiac death in apparently healthy people.

Ongoing trials in Italy and England may help answer this question, Kottke and his colleagues note.

If fish oil is as effective against fatal heart arrhythmias as evidence suggests, the researchers conclude, it would have more widespread benefits than either AEDs or implanted defibrillators.